It is known to attach condition monitoring units to a train axle or to a bearing thereof in order to monitor parameters such as vibration, temperature and acoustic emission.
Within the automotive sector, there are a plethora of wired sensors, many of which are associated with ECU (Engine Control Unit) and OBD (On Board Diagnostic) systems. These sensors are fully integrated into the vehicle's infrastructure such that during the vehicle's operation they have a continuous power supply. Data communications are supported by a CAN (Controller Area Network) bus. These sensor systems operate continuously to monitor their target parameters.
Locomotives and passenger carriages also have a range of sensor systems that are fully integrated, but these are generally related to safety critical functionality.
In applications where no network structure exists or where the condition monitoring unit has to be attached to rotating components, it has been proposed to use wireless nodes. A consideration in the design of wireless sensor systems is the time between maintenance which is frequently dictated by the life of their batteries. As a consequence, power management is an important factor in the design of wireless sensor systems because it has an immediate impact on maintenance intervals.
Currently available condition monitoring solutions with permanent power sources are configured to capture data continuously. However the captured data generally contain a large volume of artifacts and the measured curves reflect the curviness of the track, imperfections of the rails and other external influences. It is therefore necessary to use complex algorithms to filter the data to eliminate artifacts and to extract valuable and reliable information on the condition of the bearing from the large volume of data.
In order to save power and to ensure good data quality, it has been proposed to limit the measurement to specific sections of a track where low background noise and external factors are expected. To this end, it has been proposed to set predetermined waypoints triggering a measurement based on GPS data. If a certain waypoint along a track is reached, the control unit triggers a signal starting the condition monitoring units to measure the operating parameters of the bearings or other components being monitored and, likewise, the monitoring is stopped if the vehicle leaves the track.
To ensure consistent and reliable data readings, the condition monitoring unit should capture data on a known good quality section of track. Preferably, the track or route should be straight, level and allow the train to reach and maintain a constant speed. Additionally these waypoints are track trigger co-ordinates and function as reference points for data trending as all measurements will therefore be referenced to the same points on the track or route.
Energy consumption can be reduced significantly by powering on and logging data for short periods of time when the correct conditions are met. Triggering measurements on a known piece of track reduces data collection errors or anomalies and optimizes the power usage. The reduced energy consumption may enable using generators or power harvesting means with lower rated power or increase the longevity of batteries.
According to the prior art, these GPS-waypoints triggering the activation or deactivation of the sensor units or condition monitoring units are set manually in advance. This is burdensome and complicated and requires the involvement of skilled engineers having both knowledge of the geographical and technical details of the track and of the technology being monitored.